Hydrogen-selective membrane

Abstract

A hydrogen-selective membrane comprises a tubular porous ceramic support having a palladium metal layer deposited on an inside surface of the ceramic support. The thickness of the palladium layer is greater than about 10 mu m but typically less than about 20 mu m. The hydrogen permeation rate of the membrane is greater than about 1.0 moles/m2. s at a temperature of greater than about 500 DEG C. and a transmembrane pressure difference of about 1,500 kPa. Moreover, the hydrogen-to-nitrogen selectivity is greater than about 600 at a temperature of greater than about 500 DEG C. and a transmembrane pressure of about 700 kPa. Hydrogen can be separated from a mixture of gases using the membrane. The method may include the step of heating the mixture of gases to a temperature of greater than about 400 DEG C. and less than about 1000 DEG C. before the step of flowing the mixture of gases past the membrane. The mixture of gases may include ammonia. The ammonia typically is decomposed to provide nitrogen and hydrogen using a catalyst such as nickel. The catalyst may be placed inside the tubular ceramic support. The mixture of gases may be supplied by an industrial process such as the mixture of exhaust gases from the IGCC process.

We claim: 
     
       1. A method for making a membrane for selectively removing hydrogen from a mixture of gases containing hydrogen, comprising chemically depositing a uniform layer of palladium metal on the inside surface of a tubular, porous ceramic support having a pore size of greater than about 10 nm. 
     
     
       2. The method according to claim 1 wherein the layer of palladium metal has a thickness of from about 10 μm to about 20 μm. 
     
     
       3. The method according to claim 1 wherein the step of chemically depositing comprises: adsorbing a layer of colloidal tin ions on the inside surface of the porous ceramic support; and   depositing a palladium metal layer on the colloidal tin.   
     
     
       4. A method for forming a membrane for selectively removing hydrogen from a mixture of gases containing hydrogen, comprising; providing a porous, tubular ceramic support having inside and outside opposed surfaces, the ceramic support having a pore size of from about 10 nm to about 200 nm;   covering the outside surface;   applying a sensitizing material to the inside surface of the support, the sensitizing material comprising an aqueous solution of Sn (II) and Sn (IV) ions; and   applying a palladium metal layer to the inside surface.   
     
     
       5. The method according to the method of claim 4 wherein the palladium metal layer has a thickness of from about 10 μm to about 20 μm.